Packaged hot-melt pressure sensitive adhesive

ABSTRACT

The present invention relates to a packaged hot-melt pressure sensitive adhesive comprising a hot-melt pressure sensitive adhesive composition and a coextrusion coating consisting of neat low density polyethylene, neat polypropylene, or neat ethylene vinyl acetate. The present invention further relates to the use of the packaged adhesive formed as individual forms in an adhesive application process, and the use of the packaged adhesive in the production of laminated articles, including nonwoven hygiene articles, disposable medical drapes, and also laminate constructions such as tapes and labels.

This patent application claims the benefit of or priority to U.S.provisional application No. 61/828,479 filed on May 29, 2013.

FIELD OF THE INVENTION

The present invention relates to a packaged hot-melt pressure sensitiveadhesive comprising a hot-melt pressure sensitive adhesive compositionand a coextrusion coating consisting of neat low density polyethylene,neat polypropylene, or neat ethylene vinyl acetate. The presentinvention further relates to the use of the packaged adhesive formed asindividual forms in an adhesive application process, and the use of thepackaged adhesive in the production of laminated articles, includingnonwoven hygiene articles, disposable medical drapes, and also laminateconstructions such as tapes and labels.

BACKGROUND OF THE INVENTION

Hot-melt adhesive compositions are typically solid at room temperature.Therefore, said adhesive compositions are heated and are subsequentlyapplied to a substrate in a molten state, which is then placed incontact with one or more further substrates. The hot-melt adhesivecomposition cools and solidifies, thereby forming a bond between thesubstrates.

Hot-melt adhesive compositions can be used for a variety of industrialadhesive applications such as packaging and labeling, production ofnonwoven hygiene and sanitary articles, such as for the bonding ofelastics, construction and core lamination or positioning adhesive andalso for other laminates such as tapes and labels.

To prevent hot-melt adhesive compositions from agglomerating prior totheir intended use, said adhesive compositions are typically provided ina packaged form. Packaged hot-melt adhesives are typically composed of abase polymer, a tackifying agent and a wax component. The base polymerprovides the formulation with its strength and adhesive characteristics.The tackifying agent allows the polymer to be more adhesive by improvingwetting during the application, and give tack to the adhesive and alsolower the viscosity. Tack is required in most adhesive formulations toallow for proper joining of articles prior to the hot-melt adhesivesolidifying.

A great disadvantage of currently used packaged hot-melt pressuresensitive adhesives is that fusion of the several packaging materialsincreasingly leads to agglomeration of several particular forms duringstorage, which may lead to the blocking of said individual forms duringthe subsequent adhesive application processes. Such agglomeration mayprevent the use of the individual forms, because it may be verydifficult to remove the packaged hot-melt adhesive from the storagecontainer, or it may prevent an automatic or semi automatic processingof the individual forms, e.g. pillows or prills, to be fed to themelting tanks. By automating this process, the customer will havesignificantly reduced handling and be able to store the adhesive at afurther distance from the melt tank and convey with reduced operatorrequirement.

The packaging material of the hot-melt pressure sensitive adhesivetypically includes various coating materials such as various portagelinen blends and core polymers to avoid agglomeration. Currently,anti-blocking powders such as talc wax or silica are used in thedischarge of hot-melts to avoid agglomeration. However, these compoundstend to become completely absorbed over time by the hot-melt and as aresult, the residual tack reappears. Furthermore, some of the currentlyused anti-blocking agents such as silica dust are potentially harmful orcan cause serious health issues, for example, lung or respiratoryproblems.

Packaged hot-melt pressure sensitive adhesives refer to adhesives, whichform a bond when pressure is applied to attach the adhesives to theadhering substrates. Said pressure sensitive packaged adhesives areusually designed to properly attach to the adhering substrate at roomtemperature. Pressure sensitive adhesives have a tendency to fusetogether at room temperature, which might lead to agglomeration of thepressure sensitive adhesive during normal handling and might thereforeimpair the use of the corresponding adhesives. To prevent such fusionand blocking of packaged hot-melt pressure sensitive adhesives, powdersolutions are normally insufficient and said adhesives are typicallypackaged in more advanced coating material, e.g. a plastic or metalfilm.

U.S. Pat. No. 5,373,682 discloses a method for packaging hot-meltpressure sensitive adhesives into a plastic film. However, the methoddescribes packaging a molten hot-melt adhesive into a solid plastic filmand thereby does not disclosure a coextrusion process, wherein theadhesive composition and the coating are both applied in a molten state.A particular disadvantage of the process disclosed in U.S. Pat. No.5,373,682 is that packaging of a molten hot-melt adhesive into a solidplastic film results in packaged adhesives, which are not uniformlypackaged, e.g. which encompass air inclusions, which in turn may lead toan elevated blocking and fusion tendency of the packaged adhesives.

U.S. Pat. No. 7,572,494 B2 discloses a method for packaging hot-meltadhesives, in particular hot-melt pressure sensitive adhesives, whichincludes an extrusion process of a hot-melt adhesive and coextrusion ofa wax-based polymeric film compositions to surround the hot-meltadhesive. However, the coextruded wax-based polymer coating consists ofa polymer composition consisting of several different ingredients.

There remains a need in the art for packaged hot-melt pressure sensitiveadhesives, which comprise anti-blocking coatings, which improve thehandling of hot-melt adhesives and prevents agglomeration permanentlyand reliably.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a packaged hot-meltadhesive, specifically a hot-melt pressure sensitive adhesivecomposition, the individual forms of which do not fuse together oragglomerate during their packaging, transportation, storage or furtherprocessing. A further object is to provide free-flowing hot-meltpressure sensitive adhesives in individual form.

In one aspect of the invention, a packaged hot-melt adhesive isprovided, comprising a hot-melt pressure sensitive adhesive composition(a) and a coextrusion coating (b) consisting of neat low-densitypolyethylene (LDPE), neat polypropylene, or neat ethylene vinyl acetatehaving a melt flow index between about 20 g/10 min and about 300 g/10min (ASTM D 1238—190° C., 2.16 kgs).

In one embodiment of the present invention, the adhesive composition (a)comprises a base polymer selected from the group consisting ofpolyolefins, polyolefin copolymers, polyolefin/alpha-olefininterpolymers or synthetic rubbers.

In a preferred embodiment of the present invention, the adhesivecomposition (a) comprises a base polymer, which is selected from thegroup consisting of ethylene and propylene homo- or copolymers.

In a preferred embodiment, the adhesive composition (a) comprises a basepolymer, selected as ethylene-octene copolymer.

In a preferred embodiment of the present invention, the adhesivecomposition (a) comprises a base polymer, which is selected as ametallocene-synthesized polymer, preferably as a single-sitemetallocene-synthesized polymer, more preferably as ametallocene-synthesized ethylene or propylene homo- or copolymer, evenmore preferably as a metallocene-synthesized polypropylene polymer.

In a preferred embodiment of the present invention, the adhesivecomposition (a) comprises a base polymer, which is selected as ametallocene-synthesized low molecular weight polypropylene polymer.

In a preferred embodiment of the present invention, the adhesivecomposition (a) comprises a base polymer, which is selected from thegroup consisting of styrene-isoprene (SI), styrene-isoprene-styrene(SIS), styrene-butadiene-styrene (SBS),styrene-ethylene/butylene-styrene (SEBS) orstyrene-ethylene/propylene-styrene (SEPS).

A further object of the present invention is to provide packagedhot-melt adhesives which exhibit a low content of plasticizer tomaintain an adhesive composition (a) which exhibits an increasedhardness.

According to one embodiment of the present invention, the adhesivecomposition (a) additionally comprises one or more plasticizers in anamount of less than about 30 wt %, preferably less than about 20 wt %,more preferably less than about 15 wt %, even more preferably less thanabout 10 wt % and most preferably less than about 5 wt %, referring tothe total weight of the packaged adhesive.

In one embodiment of the present invention, the adhesive composition (a)additionally comprises one or more tackifying agents in an amountbetween about 5 wt % and about 75 wt %, preferably between about 10 wt %and about 60 wt %, more preferably between about 15 wt % and about 50 wt%, referring to the total weight of the packaged adhesive.

An object of the present invention is to provide packaged hot-meltadhesives, which provide the packaged hot-melt adhesive with a reducedtackiness, while the other properties and the purity of the packagedhot-melt adhesive, i.e. the components of the hot-melt pressuresensitive adhesive composition remains unaffected. It is also an objectof the present invention to provide hot-melt particular forms which arefree-flowing and or have a substantially tack-free surface for extendedperiods of time.

In one embodiment of the present invention, the packaged hot-meltadhesive comprises a coating (b) in an amount between about 0.1 wt % andabout 5 wt %, preferably between about 0.5 wt % and about 3 wt %, morepreferably between about 1 wt % and about 2 wt/o, and most preferablybetween about 1.5 wt % and about 5 wt %, referring to the total weightof the packaged adhesive.

In one embodiment of the present invention, the packaged hot-meltadhesive comprising a coating (b), wherein the melt flow index (ASTM D1238—190° C., 2.16 kgs) of the coating (b) is between about 50 g/10 minand about 180 g/10 min, preferably between about 100 g/10 min and about170 g/10 min and most preferably about 150 g/10 min.

In one embodiment of the present invention, the packaged hot-meltadhesive comprising a coating (b) has a melt temperature (Ring and Ball,DIN EN 1427) between about 60° C. and about 150° C., preferably betweenabout 100° C. and about 140° C. and more preferably between about 120°C. and about 130° C.

In one embodiment of the present invention, the packaged hot-meltadhesive comprising a coating (b) has a room temperature density (ASTM D1505) between about 0.80 g/cm³ and about 1.00 g/cm³, preferably betweenabout 0.91 g/cm³ and about 0.93 g/cm³, and more preferably about 0.92g/cm³.

The packaged hot-melt adhesive according to the present inventionencompasses a specific parameter range, which is advantageous for thebeneficial properties of the inventive packaged hot-melt adhesive.Further advantageous embodiments of the present invention are defined inthe corresponding dependent claims.

In one embodiment of the present invention, the adhesive composition (a)has an average penetration number (PZ), which is between about 5 andabout 200, preferably between about 10 and about 100, more preferablybetween about 15 and about 80, and most preferably between about 20 andabout 70.

Another object of the present invention is to provide individual formsof the packaged hot-melt adhesive, such as pillows or prills, as definedbelow, which do not agglomerate during packaging, transportation,storage or further processing.

It would also be desirable to prevent the agglomeration of packagedhot-melt adhesives permanently. Furthermore, it would be desirable toprovide packaged hot-melt pressure sensitive adhesives, which allowseasy de-agglomeration of temporarily blocked individual forms of thepacked hot-melt adhesive, for example when high-pressure is applied tothe packaged hot-melt adhesive during transportation or storage, or whenthe packed hot-melt adhesive is transported or stored at elevated roomtemperature, for example at an average temperature of between about 25°C. and about 45° C., between about 25° C. and about 65° C., or even ofbetween about 25° C. and about 70° C.

A further object of the present invention is to provide a packagedhot-melt pressure sensitive adhesive, which does not undesirably changethe characteristics of the packaged hot-melt adhesive after melting,such as bonding performance, melt viscosity, handling, etc.

A further object of the present invention is to provide a packagedhot-melt pressure sensitive adhesive, which is environmentally safe andwhich is not harmful to health.

The object of the present invention is the provision of packagedhot-melt adhesives, which do not agglomerate and thereby block duringthe specific application processes.

According to one embodiment, the packaged hot-melt adhesive is formed ina particular form, such as a pillow or prill.

Preferably, the particular forms, such as pillows or prills havedimensions (length/width/height) which are from about 40 mm×about 30mm×about 12 mm, or about 20 mm×about 20 mm×about 20 mm, preferably about40 mm×about 20 mm×about 10 mm and most preferably about 40 mm×about 15mm×about 7 mm.

Preferably, a plurality of individual forms such as pillows or prills,do not fuse together and/or are mechanically separable to inducefree-flowing of the individual forms.

Preferably, a plurality of individual forms of a packaged hot-meltadhesive, such as pillows or prills, is used in an adhesive applicationprocess, wherein the packaged hot-melt adhesive is conveyed to a meltingsystem in a free-flowing and air conveyable form before being molten andapplied to a substrate.

According to another embodiment, the packaged hot-melt adhesive isformed in a particular form, such as a coextruded rope.

Preferably the coextruded ropes have a diameter which is between about0.1 cm and about 5 cm, preferably between about 1 cm and about 3 cm, andmore preferably about 2.5 cm.

Preferably, a plurality of individual forms of a packaged hot-meltadhesive, such as a coextruded rope, is used in an adhesive applicationprocess, wherein the packaged hot-melt adhesive is conveyed to a meltingsystem by pulling the coextruded rope through a series of pulleys insidea protective cover into the premelter.

Preferably, the plurality of individual forms such as a coextruded rope,do not fuse together and/or are mechanically separable to inducefree-flowing of the individual forms.

For individual forms, the packaged hot-melt adhesive has a free-flowingand/or air-conveyable form at ambient conditions.

According to the invention, the package hot-melt adhesive is obtained bya coextrusion process.

Preferably, the packaged hot-melt adhesive according to the presentinvention is obtained by a coextrusion process, wherein the hot-meltpressure sensitive adhesive composition (a) is pumped through thecoextrusion head and wherein the coextrusion coating (b) is added to theadhesive composition (a) such that the coextrusion coating (b)substantially covers the adhesive composition (a) as a cover sheet.

Furthermore, the packaged hot-melt adhesive is obtained by a coextrusionprocess, wherein the coextrusion process comprises:

-   -   (i) providing one or more hot-melt components and blending the        hot-melt components to form a hot-melt pressure sensitive        adhesive composition    -   (ii) providing a coating material selected from neat low-density        polyethylene, neat polypropylene, or neat ethylene vinyl acetate        having a melt flow index between about 20 g/10 min and about 300        g/10 min.    -   (iii) coextruding both (i) and (ii) such that the adhesive forms        a strand substantially surrounded by the coating material    -   (iv) optionally cutting the resulting, coated strand of adhesive        (e.g. by forcing the composition past rotating blades and        cutting the hot-melt ribbons to form resultant individual forms)    -   (v) solidifying the individuals, optionally by cooling the        individuals by a liquid cooling medium or by a dry air        circulated.

In one aspect the invention covers a method of using a hot melt pressuresensitive adhesive in individual forms comprising the steps of: a.)obtaining coextruded hot melt pressure sensitive adhesive in individualforms; and b.) conveying the hot melt pressure sensitive adhesive to amelting system by use of a conveying system selected from the groupconsisting of a tubular drag conveying system and a melt on demandconveying system.

In one embodiment, the coextruded hot melt pressure sensitive adhesivein individual form is fed into the conveying system by use of avibratory feeder. In another embodiment, the conveying system is atubular drag conveying system. In still another embodiment, the hot meltpressure sensitive adhesive in individual form is a pillow with athickness of at least about 0.635 cms (0.250 inches). Alternately, thehot melt pressure sensitive adhesive comprises a propylene polymer. Insome embodiments, the hot melt pressure sensitive adhesive has anaverage penetration number (PZ), which is between about 20 and about 70.In other embodiments, the hot melt pressure sensitive adhesive isconveyed to more than one melting system. In still other embodiments,the hot melt pressure sensitive adhesive is provided in the individualform selected from the group consisting of a pillow, a prill and acoextruded rope. In one embodiment, the hot melt pressure sensitiveadhesive composition comprises a base polymer selected from the groupconsisting of polyolefins, polyolefin copolymers,polyolefin/alpha-olefin interpolymers and synthetic rubbers.

In one aspect, the invention provides a method of providing moltenadhesive comprising: a. providing a plurality of individual forms of acoextrusion coated hot melt pressure sensitive adhesive wherein the hotmelt pressure sensitive adhesive has an average penetration number (PZ),which is between about 20 and about 70; b. conveying the plurality ofindividual forms to a melting system; c. heating the plurality ofindividual forms until they become a molten adhesive; and d. applyingthe molten adhesive to a substrate.

In one embodiment, the plurality of individual forms have a rating of atleast 3 when tested according to blocking test 1. In another embodiment,the plurality of individual forms are continuously conveyed to themelting system so as to maintain a consistent level of adhesive in themelting system. In still another embodiment, the plurality of individualforms are conveyed with a tubular drag conveying system, or alternatelya melt on demand conveying system.

In one embodiment, the coextrusion coating is neat low-densitypolyethylene. In another embodiment, the neat low-density polyethylenehas a melt flow index (ASTM D 1238—190° C., 2.16 kgs) between about 20g/10 min and about 300 g/10 min. In still another embodiment, the hotmelt pressure sensitive adhesive comprises a propylene polymer. In oneembodiment, the substrate is a non-woven. In other embodiments, the hotmelt pressure sensitive adhesive has an average penetration number (PZ),which is between about 20 and about 70. In still other embodiments, thehot melt pressure sensitive adhesive composition comprises ametallocene-synthesized low molecular weight polypropylene polymer.

In a preferred use of the invention, the packaged hot-melt adhesive isused for the production of hygiene and sanitary articles, non-wovenarticles, labeling, elastic lamination, construction lamination or aspositioning adhesive. Preferably, the packaged hot-melt adhesive is usedfor the production of nonwoven hygiene articles including the productionof diapers, adult incontinence devices, sanitary napkins, medical drapesand also laminate constructions such as tapes and labels.

In one aspect, the present invention is directed to an adhesivecontaining container comprising a plurality of individual forms of thepackaged hot-melt adhesive according to the present invention, whereinthe container is selected from at least one of a box, preferably aplastic bag, a pouch, a big bag, and a supersack.

FIGURES

FIG. 1: Schematic representation of a vacuum-conveying system.

Packaged hot-melt pressure sensitive adhesive is inserted into a feedhopper, is introduced into the vacuum-conveying system by a vibratoryfeeder and is filled into a series of hot-melt tanks, through adischarge valve, which is controlled by electronic level probes.

FIG. 2: Schematic representation of a tubular drag-conveying system.

Packaged hot-melt pressure sensitive adhesive is inserted into a tubulardrag-conveying system by a vibratory feeder, wherein the adhesive isconveyed to a plurality of hot-melt tanks by a disc-distribution system,which is controlled by electronic level probes.

DETAILED DESCRIPTION OF THE INVENTION

In one aspect of the present invention, a packaged hot-melt adhesive isprovided, comprising a hot-melt pressure sensitive adhesive composition(a) and a coextrusion coating (b) consisting of neat low-densitypolyethylene, neat polypropylene, or neat ethylene vinyl acetate havinga melt flow index between about 20 g/10 min and about 300 g/10 min.

In a further aspect of the present invention, a plurality of individualforms of a packaged adhesive in accordance with the present inventionare provided, which may be used in an adhesive application process,wherein the packaged adhesive is conveyed to a melting system in afree-flowing and air conveyable form before being molten and applied toa substrate.

In the following, the hot-melt pressure sensitive adhesive composition(a) and the coextrusion coating (b), and the anti-blockingcharacteristics of the packaged hot-melt adhesive, e.g. the individualforms, will be described in more detail, as well as individual formscomprising said packaged hot-melt adhesive.

Unless otherwise specified, the following abbreviations and definitionsare used in the context of the present invention.

The undefined article “a” or “an” means one or more of the speciesdesignated by the term following said article. For example, “aindividual form” encompasses one or more individual forms.

The term “about” in the context of the present application means a valuewithin 15% (±15%) of the value recited immediately after the term“about,” including any numeric value within this range, the value equalto the upper limit (i.e., +15%) and the value equal to the lower limit(i.e., −15%) of this range. For example, the phrase “about 100”encompasses any numeric value that is between 85 and 115, including 85and 115 (with the exception of “about 100%”, which always has an upperlimit of 100%). A further exception is the phrase “about 0” or “about0%”, which always has a lower limit of 0 or 0%). In a preferred aspect,“about” means ±10%, even more preferably ±5%, even more preferably ±1%or less than ±%.

The amount of a specific component, which is added to packaged hot-meltadhesive comprising a hot-melt pressure sensitive adhesive composition(a) and a coextrusion coating (b) may be defined as the weight perweight percentage as defined by the following ratio: wt %=(g of specificcomponent)/(g of composition comprising specific components). Forexample, when 2.5 g of plasticizer in 100 g of a packaged hot-meltadhesive are used, this results in a ratio of 2.5 wt % (2.5/100) ofplasticizer.

For the purpose of the present invention, the term “hot-melt” or“hot-melt composition” refers to a solvent free product which is more orless solid at room temperature, e.g. at a temperature between about 20°C. and about 25° C. When heated the hot-melt becomes tacky andpreferably liquid (molten) and can be applied, for example to asubstrate to provide an adhesive surface.

The hot-melt adhesive composition (a) of the present invention is ahot-melt “pressure sensitive adhesive” composition. The term“pressure-sensitive adhesive” means an adhesive that is aggressively andpermanently tacky at room temperature and firmly adheres to a variety ofdissimilar surfaces upon mere contact without the need of more thanfinger or hand pressure, i.e. a hot-melt adhesive composition thatretains surface tackiness over time including when cooled.

A. The Hot-Melt Pressure Sensitive Adhesive Composition (a)

A hot-melt pressure sensitive adhesive typically comprises at least onethermoplastic base polymer, at least one plasticizer and at least onetackifying agent.

Generally, the invention's hot-melts will additionally contain one ormore tackifying resins, plasticizers or oils and optionally waxes pluscustomary additives and adjutants such as stabilizers, antioxidants,pigments, UV stabilizers or absorbers, fillers etc. Materials used inhot-melt adhesives are known.

The packaged hot-melt adhesive according to the present inventioncomprises a hot-melt pressure sensitive adhesive composition (a), whichpredominantly determines the adhesive properties of the packagedhot-melt adhesive.

The hot-melt pressure sensitive adhesive composition (a) comprises abase polymer. The present invention is not specifically limited withrespect to the base polymer being used. Rather, any polymer that inprinciple can be used in hot-melt compositions is suitable according tothe present invention. Typically, base polymers include thermoplasticpolymers selected from e.g. polyolefins, polyolefin copolymers orpolyolefin/alpha-olefin interpolymers, as well as amorphouspoly-α-olefins such as atactic propylene, and propylene copolymers withethylene, butene, hexene, and octane, or ethylene and propylene homo- orcopolymers and mixtures thereof. Also useful are polyamides andpolyesters, polyurethanes, or synthetic rubbers, such as styrene blockcopolymers.

The hot-melt pressure sensitive adhesive composition (a) will preferablycomprise at least one ethylene polymer, and may comprise a blend of twoor more polymers. The term ethylene polymer as used herein refers tohomopolymers, copolymers and terpolymers of ethylene.

In the present invention, the base polymer can be selected from thegroup consisting of ethylene copolymers. In a preferred embodiment, thebase polymer is selected as ethylene vinyl acetate, ethylene methylacrylate, ethylene n-butyl acrylate, ethylene n-hexyl acrylate,ethylene-2-ethylhexyl acrylate, ethylene butene, ethylene octene,ethylene acrylic acid, or ethylene methacrylic acid copolymers. Evenmore preferred, the base polymer is selected as ethylene-octenecopolymer.

Also, the base polymer is selected from the group consisting ofpolyolefin/alpha-olefin interpolymers, in particular ethylenecopolymers, such as ethylene-octene. A particular preferred polymer suchas ethylene octene has a melt flow index between about 0.1 g/10 min andabout 4,000 g/10 min, preferably between about 1 g/10 min and about 10g/10 min and most preferably about 5 g/10 min. A particular preferredpolymer such as ethylene octene has a density between about 0.7 g/cm³and about 1.0 g/cm³, preferably between about 0.8 g/cm³ and about 0.9g/cm³, most preferably about 0.87 g/cm³. More than one ethylenecopolymer may be used to optimize the melt flow index and density of thepolymer. A preferred example of ethylene copolymer includes ENGAGE 8200available from Dow Chemical Company, US. A second polymer may be addedin addition to the first to further optimize properties e.g. an ethylenevinyl acetate polymer may be used in combination with ethylene octene.

In another option of the present invention, the base polymer can beselected as a low molecular weight polypropylene polymer. These basepolymers can either be homopolymers of propylene or copolymers ofpropylene with one or more α-olefin comonomer, such as for exampleethylene, 1-butene, 1-hexene, or 1-octene. The average molecular weightof the low molecular weight polypropylene polymers in the scope of thepresent invention may be in the range between about 4,000 g/mol andabout 150,000 g/mol, preferably between about 10,000 g/mol and about100,000 g/mol, more preferably between about 30,000 g/mol and about60,000 g/mol and most preferably about 45,000 g/mol. Said polymers mayhave a Vicat softening point between about 80° C. and about 170° C.,preferably about 90° C. Polypropylene polymers are usually predominantlyamorphous without a well-defined melting point. Preferred examples ofpolypropylene homopolymers or copolymers of propylene include VISTAMAX6202 available from EXXON MOBILE CHEMICALS, US and MODU S-400 availablefrom Idemitsu Kosan Co., JP.

Other polymers that may be useful in the hot-melt composition of thepresent invention include so-called metallocene or single-site catalyzedpolymers, including homopolymers and interpolymers of ethylene,propylene, or butane including homopolymers and interpolymers ofethylene with at least one C₂ to C₂₀-α-olefin. In a preferred option,the basic polymer is selected as a metallocene-synthesized low molecularweight polypropylene polymer. Metallocene polymers are prepared using aconstrained geometry or single site metallocene catalyst. Usefulmetallocene polymers include, e.g. a homogeneous linear or substantiallylinear polymers that are interpolymers of ethylene and at least oneC₃-C₂₀-α-olefin including e.g., ethylene/α-olefin/diene terpolymers. Theterm “homogenous” as used with respect to the metallocene polymerindicates that any comonomer is randomly distributed within a giveninterpolymer molecule and substantially all of the interpolymermolecules have the same ethylene/comonomer ratio within thatinterpolymer. Linear ethylene interpolymers are interpolymers that havean interpolymer backbone substituted with less than 0.01 long chainbranches per 1000 carbons. The substantially linear ethyleneinterpolymers are interpolymers that include long chain branching. Thelong chain branches have the same comonomer distribution as the polymerbackbone and can be as long as about the same length as the length ofthe polymer backbone. Suitable substantially linear ethyleneinterpolymers have a polymer backbone substituted with from about 0.1 toabout 3 long chain branches per 1000 carbons. Useful C₃-C₂₀-α-olefinsused in the preparation of ethylene interpolymers include, e.g.,propylene, isobutylene, 1-butene, 1-hexene, 4-methyl-1-pentene,I-heptene, I-octene, cyclopentene, cyclohexene, cyclooctene andcombinations thereof. The dienes suitable as comonomers, particularly inthe making of ethylene/α-olefin/diene terpolymers, are typicallynon-conjugated dienes having from 6 to 15 carbon atoms. Useful examplesof suitable non-conjugated dienes include: (1) straight chain acyclicdienes including, e.g., 1,4-hexadiene, 1,5-heptadiene, and1,6-octadiene; (2) branched chain acyclic dienes including, e.g.,5-methyl-1,4-hexadiene, 3,7-dimethyl-1,6-octadiene, and3,7-dimethyl-1,7-octadiene, (3) single ring alicyclic dienes including,e.g., 4-vinylcyclohexene, 1-allyl-4-isopropylidene cyclohexane,3-allylcyclopentene, 4-allyl cyclohexene, and1-isopropenyl-4-butenylcyclohexene; and (4) multi-ring alicyclic fusedand bridged ring dienes including, e.g., dicyclopentadiene, andcycloalkylidene-substituted norbornenes including, e.g.,5-methylene-2-norboraene, 5-methylene-6-methyl-2-norbornene,5-methylene-6,6-dimethyl-2-norbornene, 5-propenyl-2-norbornene,5-(3-cyclopentenyl)-2-norbornene, 5-ethylidene-2-norbornene, and5-cyclohexylidene-2-norbornene. Useful homogenous linear orsubstantially linear ethylene polymers have a narrow molecular weightdistribution (M_(w)/M_(n)) including, e.g., from 1.5 to 3.5, or evenfrom 1.8 to 2.8.

Examples of useful metallocene polymers are described in U.S. Pat. Nos.5,324,800, 5,548,014, 5,530,054 and 6,207,748 and incorporated herein.

Useful metallocene polymers are commercially available under theAFFINITY series of trade designations including EG 8200 polyolefinplastomer from Dow Chemical Company (Midland, Mich.), and linearethylene polymers are commercially available under the EXACT series oftrade designations from ExxonMobil (Texas).

The metallocene polymer is preferably present in the hot-melt adhesivecomposition in an amount from about 0% wt % to about 80 wt %, from about5% wt % to about 70 wt %/o, from about 10 wt % to about 60 wt %, or evenfrom about 15 wt % to about 50 wt %. In some embodiments the amount ofmetallocene polymer, which is present in the hot-melt adhesivecomposition may be higher, preferably up to about 90 wt % and morepreferably the hot-melt adhesive composition may be neat metallocenepolymer.

Metallocene polymer present in the adhesive composition (a) may exhibitsome degree of crystallinity. For example, there are some grades ofcommercial low molecular weight polypropylene polymers having a lowdegree of crystallinity. Preferably, the adhesive composition (a) has alow degree of crystallinity and the coextrusion coating (b) according tothe present invention has a high degree of crystallinity.

One other class of thermoplastic base polymers suitable for use in thepressure-sensitive hot-melt adhesive composition (a) together with thecoextrusion coating (b) is thermoplastic elastomers. Suitablethermoplastic elastomers include block copolymers having at least one Ablock that includes a vinyl aromatic compound and at least one B blockthat includes an elastomeric conjugated diene, including hydrogenated,unhydrogenated conjugated dienes, and combinations thereof. The A blocksand the B blocks may bind to one another in any manner of binding suchthat the resulting copolymer is random, block, straight-chained,branched, radial, or a combination thereof. The block copolymer canexhibit any form including, e.g., linear A-B block, linear A-B-A block,linear A-(B-A)n-B multi-block, and radial (A-B)n-Y block where Y is amultivalent compound and n is an integer of at least 3, tetrablockcopolymer, e.g., A-B-A-B, and pentablock copolymers having a structureof A-B-A-B-A. The adhesive composition can include blends of at leasttwo different block copolymers.

Useful vinyl aromatic compounds include, e.g., styrene,alpha-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene,p-tert-butylstyrene, 2,4-dimethylstyrene, 2,4,6-trimethylstyrene,diphenylethylenes including stilbene, vinyl naphthalene,vinylanthracene, vinyltoluene (a mixture of meta- and para-isomers ofmethylstyrene), vinylxylene, and combinations thereof. Suitableconjugated dienes include, e.g., butadiene (e.g., polybutadiene),isoprene (e.g., polyisoprene), 2,3-dimethyl-1,3-butadiene,1,3-pentadiene, 1,3-hexadiene, and combinations thereof, andhydrogenated versions thereof including, e.g., ethylene, propylene,butylene and combinations thereof.

Useful block copolymers include polyvinyl aromatic in an amount betweenabout 0 wt % and about 50 wt %, between about 5 wt % and about 50 wt %,between about 15 wt % and about 35 wt %, or even between about 20 wt %and about 30 wt %. Suitable block copolymers have a melt flow indexbetween about 3 g/10 min and about 50 g/10 min, or between about 5 g/10min and about 20 g/10 min, as determined by ASTM-D 1238.

The A block can also include a small amount (e.g. no greater than 10 wt% based on the weight of the A block) of a structural unit derived fromunsaturated monomers other than the vinyl aromatic compounds including,e.g., I-butene, pentene, hexene, butadiene, isoprene, methyl vinylether, methyl methacrylate, vinyl acetate and combinations thereof. TheB block can also include a small amount (e.g., no greater than 10 wt %based on the amount of the B block) of a structural unit derived fromunsaturated monomers other than the conjugated diene including, e.g.,I-butene, I-pentene, 1-hexene, methyl vinyl ether, styrene, methylmethacrylate, and combinations thereof.

Useful elastomeric polymers include, e.g., rubber (polyisoprene),polybutadiene, synthetic polyisoprene, random styrene-butadienepolymers, styrene-butadiene block copolymers, multiarmed and repeatingstyrene-butadiene copolymers, styrene-butadiene-styrene blockcopolymers, styrene-isoprene block copolymers, styrene-isoprene-styreneblock copolymers, styrene-multiarmed styrene-isoprene (SI)_(x) blockcopolymers, styrene-ethylene-butylene-styrene block copolymers,styrene-isobutylene-styrene block copolymers,styrene-ethylene-ethylene-propylene-styrene block copolymers,styrene-ethylene-propylene-styrene block copolymers and combinationsthereof.

Useful block copolymers are commercially available under the KRATON Dand G series of trade designations from Shell Chemical Company (Houston,Tex.) including, e.g., KRATON D 1163 and 1117 and KRATON G 1652 and1726, EUROPRENE Sol T trade designation from EniChem (Houston, Tex.),SEPTON trade designation from Septon Company of America (Pasadena, Tex.)including SEPTON S 1001 styrene-ethylene-propylene-styrene blockcopolymer, and SEPTON 4030, 4033, 4044, 4055 and 4077 block copolymers,and VECTOR series of trade designations from Dexco (Houston, Tex.)including VECTOR 4211 styrene-isoprene-styrene block copolymer.

The elastomer is present in the adhesive composition in an amountbetween about 0 wt % and about 35 wt %, between about 5 wt % and about35 wt %, between about 10 wt % and about 30 wt %, or even between about15 wt % and about 25 wt %.

Alternatively, the base polymer can be selected from the groupconsisting of synthetic rubbers. Preferably, the base polymer isselected from the group consisting of butadiene styrene,styrene-acrylonitrile, acrylonitrile-butadiene-styrene,styrene-butadiene rubbers, butadiene-styrene elastomers,styrene-isoprene (SI), styrene-isoprene-styrene (SIS),styrene-butadiene-styrene (SBS), styrene-ethylene/butylene-styrene(SEBS) or styrene-ethylene/propylene-styrene (SEPS). More preferred, thebase polymer is selected from the group consisting of styrene-isoprene(SI), styrene-isoprene-styrene (SIS), styrene-butadiene-styrene (SBS),styrene-ethylene/butylene-styrene (SEBS) orstyrene-ethylene/propylene-styrene (SEPS).

In a preferred embodiment the synthetic rubbers have melt flow indexbetween about 0.1 g/10 min and about 4,000 g/10 min, preferably betweenabout 10 g/10 min and about 60 g/10 min and most preferably betweenabout 25 g/10 min and about 40 g/10 min. A particular preferred polymersuch as styrene-isoprene (SI) or styrene-isoprene-styrene (SIS) has adensity between about 0.8 g/cm³ and about 1.0 g/cm³, preferably betweenabout 0.92 g/cm³ and about 0.96 g/cm³. More than one styrene-isoprene(SI) or styrene-isoprene-styrene (SIS) may be used to optimize the meltflow index and density of the polymer. Preferred examples ofstyrene-isoprene (SI) or styrene-isoprene-styrene (SIS) include KRATOND1117 and KRATON D11161 NS, available from Kraton Polymers, US, VECTOR4114A and VECTOR 4411 A from Dexco Polymers, USA.

The base polymers according to the present invention may befunctionalized, e.g. by using (co-)monomers with at least one functionalgroup, e.g. by an unsaturated monomer, which is functionalized bycarboxylic acids, dicarboxylic acids, organic esters, organicanhydrides, organic alcohols, organic acid halides, organic peroxides,amides or imides.

An object of the present invention is to provide a packaged hot-meltadhesive, which provides an increased structural resistance of theadhesive, which is referred hereto as hardness.

A measure of the hardness of a specific material is obtained by allowinga weighted needle of specified dimensions to penetrate into the materialunder specific test conditions, e.g. at a defined temperature. Thepenetration number (PZ) is usually recorded as the number of units ofdepth which the needle penetrates in a given time. The harder a specificmaterial, the lower is its penetration number. The penetration numberaccording to the present invention is determined by needle penetrationaccording to the test procedure is described in DIN 51579 at atemperature of 25° C. (see also examples section).

In accordance with the present invention, the packaged hot-melt adhesivehas an average penetration number (PZ), which is between about 5 andabout 200, preferably between about 10 and about 100, more preferablybetween about 15 and about 80, and most preferably between about 20 andabout 70.

Another parameter to determine the properties of a packaged hot-meltadhesive according to the present invention is the viscosity. Typicallypolymers partially display non-Newtonian viscosity properties. Thismeans that their viscosity does not remain constant over a given rangeof shear rates. Polymer viscosity rates are typically referred to incorrelation with the corresponding temperature, wherein said viscosityrates have been measured. The polymer viscosity according to the presentinvention is determined according to method ASTM D-3236 (see alsoexamples section).

The hot-melt pressure sensitive adhesive composition (a) according tothe present invention can be formulated to exhibit a suitable viscosity.Useful packaged hot-melt adhesives according to the present inventionexhibit a viscosity measured at 150° C. of between about 200 mPas andabout 20,000 mPas, preferably between about 500 mPas and about 10,000mPas, more preferably between about 100 mPas and about 5,000 mPas andmost preferably between about 2,000 mPas and about 4,000 mPas.

The packaged hot-melt adhesive according to the present inventioncomprises a hot-melt pressure sensitive adhesive composition (a) and acoextrusion coating (b), which typically consist of different materials,which in turn may have different viscosities.

The packaged hot-melt adhesive according to the present invention ischaracterized by various parameters. The melting point of the packagedadhesive according to the present invention is determined by the Ringand Ball method (DIN EN 1427) (see Example section).

The packaged adhesive according to the present invention may have amelting point according to DIN EN 1427 between about 60° C. and about130° C., preferably between about 70° C. and 110° C.

Also, the packaged adhesive according to the present invention may havea room temperature density between about 0.80 g/cm³ and about 1.00g/cm³, preferably between about 0.85 g/cm³ and about 0.95 g/cm³ and morepreferably about 0.91 g/cm³.

The packaged hot-melt adhesive comprising a hot-melt pressure sensitiveadhesive composition (a) may additionally comprise further, optional,additives such as tackifying agents, plasticizers, stabilizers,antioxidants, pigments, dyes, ultraviolet light absorbers, anti-slipagents and combinations thereof.

In one aspect of the present invention, the packaged hot-melt adhesivecomprising a hot-melt pressure sensitive adhesive composition (a) and acoextrusion coating (b) additionally comprises one or more plasticizers.

Suitable plasticizers may include naphthenic oils, paraffinic oils(e.g., cycloparaffin oils), mineral based oils, phthalate esters,adipate esters, olefin oligomers (e.g., oligomers of polypropylene,polybutene, and hydrogenated polyisoprene), polybutenes, polyisoprene,hydrogenated polyisoprene, polybutadiene, benzoate esters, animal oil,plant oils (e.g. castor oil, soybean oil), derivatives of oils, glycerolesters of fatty acids, polyesters, polyethers, lactic acid derivativesand combinations thereof. A “plasticizer” in the meaning of the presentinvention is a typically organic composition that can be added tothermoplastics, rubbers and other resins to improve extrudability,flexibility, workability and stretchability in the finished adhesive.Any material which flows at ambient temperatures and is compatible withthe block copolymer may be useful. The most commonly used plasticizersare oils which are primarily hydrocarbon oils that are low in aromaticcontent and are paraffinic or naphthenic in character. The oils arepreferably low in volatility, transparent and have as little color andodor as possible. Furthermore, olefin oligomers, low molecular weightpolymers, vegetable oils and their derivatives and similar plasticizingoils may be used as plasticizers.

Also, the plasticizer can be selected from the group consisting ofnapthenic process oils and paraffinic process oils, such as NYFLEX 222Bavailable from Nynas AB, SE and KRYSTOL 550 available from PetrochemCarless Ltd., UK.

Useful commercially available plasticizers include KAYDOL OIL fromSonneborn (Tarrytown N.Y.) PARAPOL polybutene from Exxon Mobil ChemicalCompany (Houston, Tex.), OPPANOL polyisobutylene from BASF(Ludwigsjhafen, Germany), KRYSTOL 550 mineral oil from Petrochem CarlessLimited (Surrey, England) and PURETOL 15 mineral oil from Petro CanadaLubricants Inc. (Mississauga, Ontario).

Preferably, the amount of plasticizer in the hot-melt pressure sensitiveadhesive composition (a) is less than about 30 wt % referring to thetotal weight of the packaged hot-melt adhesive, more preferably lessthan about 20 wt %, even more preferably less than about 15 wt %, evenmore preferably less than about 10 wt %, and most preferably less thanabout 5 wt %.

The packaged hot-melt adhesive comprising a hot-melt pressure sensitiveadhesive composition (a) and a coextrusion coating (b) may additionallyor alternatively comprise one or more tackifying agents.

The tackifying agent can be at least partially hydrogenated in order toimprove stability for bulk handling. Useful tackifying agents have Ringand Ball softening point of less than about 140° C., less than about130° C., less than about 100° C., or even between about 100° C. to about140° C. The tackifying agent can be fluid or solid at room temperature.Suitable classes of tackifying agents include, e.g., aromatic, aliphaticand cycloaliphatic hydrocarbon resins, mixed aromatic and aliphaticmodified hydrocarbon resins, aromatic modified aliphatic hydrocarbonresins, and hydrogenated versions thereof; terpenes, modified terpenesand hydrogenated versions thereof; natural rosins, modified rosins,rosin esters, and hydrogenated versions thereof; low molecular weightpolylactic acid; and combinations thereof. Examples of useful naturaland modified rosins include gum rosin, wood rosin, tall oil rosin,distilled rosin, hydrogenated rosin, dimerized rosin and polymerizedrosin. Examples of useful rosin esters include e.g., glycerol esters ofpale wood rosin, glycerol esters of hydrogenated rosin, glycerol estersof polymerized rosin, pentaerythritol esters of natural and modifiedrosins including pentaerythritol esters of pale wood rosin,pentaerythritol esters of hydrogenated rosin, pentaerythritol esters oftall oil rosin, and phenolic-modified pentaerythritol esters of rosin.

Examples of useful polyterpene resins include polyterpene resins havinga melting point, as determined by DIN EN 1427 (Ring and Ball) of fromabout 10° C. to about 180° C., hydrogenated polyterpene resins, andcopolymers and terpolymers of natural terpenes (e.g. styrene-terpene,alpha-methyl styrene-terpene and vinyl toluene-terpene). Examples ofuseful aliphatic and cycloaliphatic petroleum hydrocarbon resins includealiphatic and cycloaliphatic petroleum hydrocarbon resins having Ringand Ball softening points of from about 10° C. to about 140° C. (e.g.,branched and unbranched C5 resins, C9 resins, and C10 resins) and thehydrogenated derivatives thereof.

Useful tackifying agents are commercially available under a variety oftrade designations including, e.g., the ESCOREZ series of tradedesignations from Exxon Mobil Chemical Company (Houston, Tex.) includingESCOREZ 1310 LC, ESCOREZ 5400, ESCOREZ 5415, ESCOREZ 5600, ESCOREZ 5615,and ESCOREZ 5690, the EASTOTAC series of trade designations from EastmanChemical (Kingsport, Tenn.) including EASTOTAC H-100R, EASTOTAC H-100L,and EASTOTAC H130W, the WINGTACK series of trade designations from CrayValley HSC (Exton, Pa.) including WINGTACK 86, WINGTACK EXTRA, andWINGTACK 95, the PICCOTAC and KRISTALEX series of trade designationsfrom Eastman Chemical Company (Kingsport, Tenn.) including, e.g.,PICCOTAC 8095 and KRISTALEX 3100, ARKON M-100 of trade designations fromArakawa Europe GmbH, Germany, SUKOREZ SU-100 of trade designations fromKolon Industries Inc., Korea, and SYLVARES 7115 and SYLVARES SA 140 oftrade designatons from Arizona Chemical, USA.

Preferably, the amount of tackifying agent in the hot-melt pressuresensitive adhesive composition (a) is between about 5 wt % and about 75wt %, preferably between about 10 wt % and about 60 wt %, morepreferably between about 15 wt % and about 50 wt %, referring to thetotal weight of the packaged adhesive.

The packaged hot-melt adhesive comprising a hot-melt pressure sensitiveadhesive composition (a) and a coextrusion coating (b) may additionallyor alternatively comprise one or more antixodiants and/or morestabilizers.

Useful antioxidants are, e.g., high molecular weight hindered phenolsand multifunctional phenols. Useful stabilizers are, e.g., phosphites,such as tris-(p-nonylphenyl)-phosphite (TNPP) andbis(2,4-di-tert-butylphenyl)4,4′-diphenylene-diphosphonite anddi-stearyl-3,3′-thiodipropionate (DSTDP). Useful antioxidants are, e.g.,commercially available under trade designation IRGANOX, includingIRGANOX 1010, from Ciba (Terrytown, N.Y.), and under the tradedesignation BNX, including BXN 1010, from Mayzo, Inc. (Norcross, Ga.).Useful anti-slip agents are, e.g., silicone oils. Examples thereof arecommercially available, e.g., under the trade designation Tegiloxan andavailable from Goldschmidt Industrial Specialties.

The amount of antioxidant and/or stabilizer in the hot-melt pressuresensitive adhesive composition (a) may be between about 0.1 wt % andabout 5.0 wt % referring to the total weight of the packaged hot-meltadhesive, more between about 0.1 wt % and about 3.0 wt %, morepreferably between about 0.1 wt % and about 2.0 wt % even morepreferably less than about 0.2 wt % and about 1 wt %.

B. The Coextrusion Coating (b)

According to the present invention, the packaged hot-melt adhesivecomprises a coextrusion coating (b), which provides for theanti-blocking properties of the packaged hot-melt adhesive.

The inventors surprisingly found out that the coextrusion coating (b) asdefined in the present invention, which is made of neat polymers insteadof conventionally used compounded coextrusion material, effectivelyprevents the agglomeration of packaged hot-melt adhesives, e.g.individual forms, over extended periods of time. Furthermore, theaddition of a coextrusion coating (b) to a hot-melt pressure sensitiveadhesive composition (a) allows for an easy de-agglomeration ofpotentially blocked individual forms. It was also found that coextrudedcoatings (b) are particularly useful for the anti-blocking properties ofpolyolefins, polyolefin copolymers or polyolefin/alpha-olefininterpolymers, as well as amorphous poly-α-olefins, which typicallypossess some residual or permanent tack, particularly at elevatedambient temperatures. In particular, the inventors found that theanti-blocking properties of the coextrusion coating (b) of the packagedhot-melt adhesive are not adversely affected when the hot-melt isexposed to higher ambient temperatures (e.g. between about 25° C. andabout 70° C.), for example during storage or transportation. This makesthe anti-blocking properties of the inventive coextrusion coating (b)very reliable.

To provide hot-melt pressure sensitive adhesives with anti-blockingproperties, powdered coating materials or compounded coextrusion coatingare conventionally applied.

Powdered coating materials are conventionally loaded onto the hot-meltpressure sensitive adhesive in a subsequent step after adhesiveformation. A major problem for hot-melt pressure sensitive adhesiveswith powdered coating materials is that the diffusion of the componentsof the powdered coating material into the adhesive may occur over time.Such a diffusion of components into the adhesive may alter thecomposition of the adhesive significantly, which in turn might impairthe functional properties of the adhesive and the anti-blocking propertyis lost during extended storage.

Some compounded coextrusion coatings are known. Compounded coextrusioncoatings are typically coextruded with the adhesive composition andtypically consist of various components, which in their combinationprovide for the anti-blocking and anti-tacking properties of thehot-melt pressure sensitive adhesive. Problems with migration ofingredients of the compounded coextrusion coatings occurs to a lesserextended in comparison to powdered coating material, but migration ofcomponents from the compounded coextrusion coating into the hot-meltpressure sensitive adhesive composition continues to pose a majorproblem for compounded coextrusion coatings, especially during long-termstorage.

The coextrusion coating (b) according to the present invention providessignificant advantages in comparison with conventional usedanti-blocking additives, which are conventionally added to thecorresponding adhesive composition, such as powdered coating materialsor compounded coextrusion coatings. A major difference between thedifferent systems is that the coextrusion coating (b) according to thepresent invention is applied to the hot-melt pressure sensitive adhesivecomposition (a) during the coextrusion process, by coextruding ahot-melt pressure sensitive adhesive composition (a) together with thecoating (b). Thereby, the coextrusion process according to the presentinvention does not require an additional step of adding anti-blockingagents, but instead allows for the provision of the packaged hot-meltadhesive according to the present invention in a one-step process.

Another important aspect of the coextrusion coating (b) of the presentinvention is that the coating consists of “neat” polymers.

Without being bound to a specific theory, it is believed that theeffectiveness of the anti-blocking properties of the coextrusion coating(b) is a result of the chemical and physical characteristics of the neatcoating film materials. This is supported by the fact that thecoextrusion coating (b) is not penetrated over time during storage andmigration of adhesive components into the coating is avoided. Also, withthe use of neat polymer extrusion coatings, deterioration ofanti-blocking properties of the coating by migration of components ofthe coating composition into the adhesive is excluded. In this regard itis noted that conventional powdered coated hot-melt compositions duringstorage at high room temperatures (25-70° C.) tend to “absorb” theanti-tack powders, thus deteriorating the anti-tack effectiveness. Itwas observed that this does not happen with the coextruded coating (b).

Furthermore, some of the conventional anti-blocking agents such assilica create inhalable dusts that are potentially harmful or can causeserious health issues, for example lung or respiratory problems. Thecoextruded coating (b) is not inhalable. This reduces health risks andexpenses for filters and air cleaning equipment. Consequently,coextruded coating (b) provide a favorable, environmentally friendly andsafe alternative to silica as an anti-blocking agent for individualforms of packaged hot-melt adhesives.

A particular advantage of the “neat” coating polymers in comparison topreviously used anti-tack coatings is that uniform “neat” coatingmaterial can be designed and manufactured, which can be applied todifferent adhesive compositions. Conventional anti-tack coatings havethe disadvantage that the type and amount of components present in saidanti-tack coatings have to be separately adjusted for each individualtype of adhesive composition to meet their specific properties. Incontrast, the “neat” coating polymers according to the present inventionencompass a single component, which does not diffuse into the adhesivecomposition, and could therefore be pre-designed and manufactured inlarge quantities, and be subsequently applied to a large variety ofdifferent adhesive compositions. Therefore, the use of “neat” coatingpolymers according to the present invention provides a resource- andcost-efficient way to provide coextrusion coatings for packaged hot-meltadhesives.

In one aspect of the present invention, the packaged hot-melt adhesivecomprises a hot-melt pressure sensitive adhesive composition (a) and acoextrusion coating (b) of consisting of neat low-density polyethylene,neat polypropylene, or neat ethylene vinyl acetate having a melt flowindex between about 20 g/10 min and about 300 g/10 min (ASTM D 1238—190°C., 2.16 kgs).

The term “neat” according to the present invention, which refers to neatpolymers, encompasses exclusively one type of polymer, which do notcontain any additional polymers, beside the stated polymers. Thereby,any blends of polymers with additional copolymers or additives areexcluded from the definition of “neat” polymers according to the presentinvention.

A “neat” low-density polyethylene coating (b) according to the presentinvention refers to a low-density polyethylene with a melt flow indexbetween about 20 g/10 min and about 300 g/10 min. Said “neat”low-density polyethylene has a density between about 0.80 g/cm³ andabout 1.00 g/cm³, preferably between about 0.85 g/cm³ and about 0.95g/cm³, more preferably between about 0.90 g/cm³ and about 0.93 g/cm³,even more preferably between about 0.91 g/cm³ and about 0.92 g/cm³ andmost preferably about 0.92 g/cm³. Said “neat” low-density polyethylenehas a melting point between about 60° C. and about 130° C., preferablybetween about 80° C. and 110° C. and most preferably between about 95°C. and about 110° C., which has been determined according to the ExxonMobil method.

Preferably, a “neat” low-density polyethylene coating (b) includes alow-density polyethylene with a melt flow index between about 20 g/10min and about 120 g/10 min, preferably between about 20 g/10 min andabout 60 g/10 min, more preferably between about 26 g/10 min and about40 g/10 min.

Alternatively, a “neat” low-density polyethylene coating (b) may alsoinclude a low-density polyethylene with a melt flow index between about120 g/10 min and about 300 g/10 min, preferably between about 140 g/10min and about 160 g/10 min, more preferably between about 150 g/10 min.

A neat low-density polyethylene coating (b) with a melt flow indexbetween about 20 g/10 min and about 300 g/10 min may be combined withany hot-melt pressure sensitive adhesive composition (a) according tothe present invention, preferably with an adhesive composition (a),which comprises a base polymer selected from polyolefins, polyolefincopolymers, polyolefin/alpha-olefin interpolymers, more preferablyselected from the group consisting of ethylene and propylene homo- orcopolymers.

Also preferably, a neat low-density polyethylene coating (b) accordingto the present invention may be combined with an adhesive composition(a), which comprises a base polymer selected as metallocene-synthesizedpolymer, preferably a metallocene-synthesized ethylene or propylenehomo- or copolymer, more preferably a metallocene-synthesized propylenepolymer.

Also preferably, a neat low-density polyethylene coating (b) accordingto the present invention may be combined with an adhesive composition(a), which comprises a base polymer selected as ethylene vinyl acetate.

Also preferably, a neat low-density polyethylene coating (b) accordingto the present invention may be combined with an adhesive composition(a), which comprises a base polymer selected from synthetic rubbers.

A “neat” polypropylene coating (b) according to the present inventionmay also refer to a polypropylene with a melt flow index between about20 g/10 min and about 300 g/10 min. Said “neat” polypropylene has a roomtemperature density between about 0.80 g/cm³ and about 1.00 g/cm³,preferably between about 0.85 g/cm³ and about 0.95 g/cm³, morepreferably between about 0.88 g/cm³ and about 0.92 g/cm³, even morepreferably between about 0.89 g/cm³ and about 0.91 g/cm³ and mostpreferably about 0.90 g/cm³. A preferred example of neat” low-densitypolyethylene includes EXXON Mobil PP 7905E1 Exxon Mobil Chemical.

Optionally, a “neat” polypropylene coating (b) may refer to apolypropylene with a melt flow index between about 50 g/10 min and about150 g/10 min, preferably between about 80 g/10 min and about 120 g/10min, more preferably between about 100 g/10 min.

A neat polypropylene coating (b) with a melt flow index between about 20g/10 min and about 300 g/10 min may be combined with any hot-meltpressure sensitive adhesive composition (a) according to the presentinvention, preferably with an adhesive composition (a), which comprisesa base polymer selected from polyolefins, polyolefin copolymers,polyolefin/alpha-olefin interpolymers, more preferably selected from thegroup consisting of ethylene and propylene homo- or copolymers.

Also preferably, a neat polypropylene coating (b) according to thepresent invention may be combined with an adhesive composition (a),which comprises a base polymer selected as metallocene-synthesizedpolymer, preferably a metallocene-synthesized ethylene or propylenehomo- or copolymer, more preferably a metallocene-synthesized propylenepolymer.

Also preferably, a neat polypropylene coating (b) according to thepresent invention may be combined with an adhesive composition (a),which comprises a base polymer selected as ethylene vinyl acetate.

Also preferably, a polypropylene coating (b) according to the presentinvention may be combined with an adhesive composition (a), whichcomprises a base polymer selected from synthetic rubbers.

A “neat” ethylene polyvinyl acetate (EVA) coating (b) according to thepresent invention is ethylene polyvinyl acetate with a melt flow indexbetween about 20 g/10 min and about 300 g/10 min. Said EVA polymer has aroom temperature density between about 0.80 g/cm³ and about 1.00 g/cm³,preferably between about 0.90 g/cm³ and about 0.96 g/cm³, morepreferably between about 0.91 g/cm³ and about 0.95 g/cm³ and mostpreferably about 0.935 g/cm³. In the ethylene vinyl acetate the vinylacetate content is between about 2 wt % and about 25 wt %, preferablybetween about 5 wt % and about 20 wt %, more preferably between about 10wt % and about 15 wt %. Said “neat” low-density ethylene polyvinylacetate has a melting point between about 60° C. and about 130° C.,preferably between about 70° C. and about 110° C. and most preferablybetween about 85° C. and about 95° C. A preferred example of ethylenevinyl acetate copolymers includes Ateva 1360 available by M. Holland.

A neat ethylene polyvinyl acetate coating (b) with a melt flow indexbetween about 20 g/10 min and about 300 g/10 min may be combined withany hot-melt pressure sensitive adhesive composition (a) according tothe present invention, preferably with an adhesive composition (a),which comprises a base polymer selected from polyolefins, polyolefincopolymers, polyolefin/alpha-olefin interpolymers, more preferablyselected from the group consisting of ethylene and propylene homo- orcopolymers.

Also preferably, a neat ethylene polyvinyl acetate coating (b) accordingto the present invention may be combined with an adhesive composition(a), which comprises a base polymer selected as metallocene-synthesizedpolymer, preferably a metallocene-synthesized ethylene or propylenehomo- or copolymer, more preferably a metallocene-synthesized propylenepolymer.

Also preferably, a neat ethylene polyvinyl acetate coating (b) accordingto the present invention may be combined with an adhesive composition(a), which comprises a base polymer selected as ethylene vinyl acetate.

According to the present invention, the coextrusion coating (b)comprises neat low-density polyethylene, neat polypropylene, or neatethylene vinyl acetate having a melt flow index between about 20 g/10min and about 300 g/10 min.

The melt flow index of the coextrusion coating material correlates withits physical properties. At low melt flow index of less than about 20g/10 min, the coextrusion coating material displays a high viscosity anda poor melting behaviour, which leads to a partially inhomogeneous meltand at least partially prevents proper mixing of the adhesivecomponents.

On other hand, a high melt flow index of more than 300 g/10 mincorrelates with poor anti-blocking properties, e.g. barrier properties,of the corresponding packaged adhesive, which in turn leads toindividual forms, which tend to agglomerate during the melting processand are not free-flowing.

Therefore, the melt flow index between about 20 g/10 min and about 300g/10 min of the neat low-density polyethylene, neat polypropylene, orneat ethylene vinyl acetate coating materials covers an optimal rangefor the coating (b) to display its properties.

The inventors surprisingly found that packaged hot-melt adhesiveswherein the coextrusion coating (b) consisting of neat low-densitypolyethylene, neat polypropylene, or neat ethylene vinyl acetate, whichcomprises a melt flow index between about 20 g/10 min and about 80 g/10min display excellent anti-blocking properties, e.g. barrier properties,which include particular forms of packaged hot-melt adhesives, which arefree-flowing and or have a substantially tack-free surface for extendedperiods of time. It might be advantageous to combine said coextrusioncoating materials, which comprises a melt flow index between about 20g/10 min and about 80 g/10 min with a higher plasticizer content, whichmay be added to the hot-melt pressure sensitive adhesive composition(a).

In the present invention, the coextrusion coating (b) of the packagedhot-melt adhesives in accordance with the present invention consist ofneat low-density polyethylene, neat polypropylene, or neat ethylenevinyl acetate, which comprises a melt flow index between about 20 g/10min and about 80 g/10 min, preferably between about 20 g/10 min andabout 50 g/10 min, more preferably between about 20 g/10 min and about30 g/10 min, and most preferably about 20 g/10 min.

The inventors surprisingly found out that the packaged hot-meltadhesives consisting of neat low-density polyethylene, neatpolypropylene, or neat ethylene vinyl acetate, which comprises a meltflow index between about 120 g/10 min and about 300 g/10 min display alow viscosity and an optimal normal melting behavior, leading to ahomogenous melt. It may be advantageous to combine said coextrusioncoating materials, which comprise a melt flow index between about 120g/10 min and about 300 g/10 min with a reduced amount of plasticizer,which may be included in the hot-melt pressure sensitive adhesivecomposition (a).

In the present invention, the coextrusion coating (b) of the packagedhot-melt adhesives in accordance with the present invention consist ofneat low-density polyethylene, neat polypropylene, or neat ethylenevinyl acetate, which comprises a melt flow index between about 150 g/10min and about 300 g/10 min, preferably between about 170 g/10 min andabout 280 g/10 min, more preferably between about 180 g/10 min and about250 g/10 min, and most preferably about 220 g/10 min.

The coextrusion coating (b) at least partially, preferably substantiallycompletely, covers the surface of the hot-melt pressure sensitiveadhesive composition (a), e.g. by a film layer on the surface of thehot-melt individual forms. For the purpose of the present invention, theterm “at least partially covers” means that at least 10%, preferablymore than 25%, more preferably more than 50%, and most preferably morethan 75% or more than 90% of the surface of the individual forms arecovered by the coextrusion coating (b) in accordance with the presentinvention. Most preferably, the coextrusion coating (b) completelycovers the surface of the hot-melt pressure sensitive adhesivecomposition (a).

In particular, the coextrusion coating (b) consists of a crystallinematerial, which tends to be come easily meltable. Preferably, thecoextrusion coating (b) has a high crystallinity.

In one embodiment, the coextrusion coating (b) may be present in anamount between about 0.1 wt % and about 5 wt %, referring to the totalweight of the packaged hot-melt adhesive. Preferably, the coextrusioncoating (b) may be present in amount between about 0.5 wt % and about 3wt %. More preferably, the coextrusion coating (b) may be present inamount between about 1.0 wt % and about 3.0 wt %. In an even morepreferred embodiment, the co-extrusion coating (b) may be present inamount between about 1.5 wt % and about 5.0 wt %. In an even morepreferred embodiment, the co-extrusion coating (b) may be present inamount between about 1.5 wt % and about 2.5 wt %. In a most preferredembodiment, the co-extrusion coating (b) may be present in amountbetween about 1.5 wt % and about 2.0 wt %, referring to the total weightof the packaged hot-melt adhesive.

If the base polymer present in the hot-melt pressure sensitive adhesivecomposition (a) is selected as a synthetic rubber, the coextrusioncoating (b) may be present in an amount between about 0.5 wt % and about3 wt %, preferably, between about 1.0 wt % and about 3.0 wt %, morepreferably between about 1.5 wt % and about 3.0 wt %, even morepreferably between about 1.5 wt % and about 2.5 wt % and most preferablybetween about 1.5 wt % and about 2.0 wt %, referring to the total weightof the packaged hot-melt adhesive.

If the base polymer present in the hot-melt pressure sensitive adhesivecomposition (a) is selected as a polyolefin, polyolefin copolymer,polyolefin/alpha-olefin interpolymer, the coextrusion coating (b) may bepresent in a higher amount in relation to the amount of coating (b)present if the base polymer is selected as a synthetic rubber,preferably in an amount between about 0.1 wt % and about 3 wt %, morepreferably between about 0.5 wt % and about 3 wt %/o, even morepreferably between about 1.0 wt % and about 3 wt %, even more preferablybetween about 1.0 wt % and about 2.5 wt %, even more preferably betweenabout 1.0 wt % and about 2.0 wt % and most preferably between about 1.5wt % and about 2.0 wt %, referring to the total weight of the packagedhot-melt adhesive.

The coextrusion coating (b) may have a melting temperature between about60° C. and about 170° C., between about 60° C. and about 150° C.,preferably between about 100° C. and about 140° C. and more preferablybetween about 120° C. and about 130° C. The melting temperature has beenmeasured according to the Ring and Ball softening point method (DIN EN1427).

The coextrusion coating (b) may have a room temperature density betweenabout 0.80 g/cm³ and about 1.00 g/cm³, preferably between about 0.91g/cm³ and about 0.93 g/cm³ and more preferably about 0.92 g/cm³.

C. Individual Forms

The packaged hot-melt adhesives according to the present invention maybe in any form suitable for their use, including any “individual forms”,irrespective of size. For the purpose of the present invention the term“individual forms” comprise packaged hot-melt adhesives in the form ofgranules, blocks, pillows, prills. For another purpose of the presentinvention the term “individual forms” comprise elongated ropes or rods,or any other known form of hot-melts. The elongated ropes or rods can beof any length, and, e.g., can be wound onto a reel, spool or can befreely laid inside a box or other container and applied from there.Preferred “individual forms” such as blocks, pillows, elongated ropes orrods may have a size, in the longest dimension, in the range ofcentimeters, for example up to about 15 cm or up to about 20 cm. Incertain embodiments, the packaged hot-melt adhesives are in the form ofsmaller sized “individual forms”, such as particles, prills, chips,flakes, spheres, beads, slugs, e.g. sausage shaped slugs, or pellets.

The “individual forms” may be selected from a plurality of pillows orprills. A “prill” in the meaning of the present invention refers to asubstantially spherical bead, while a “pillow” refers to a substantialprismatic geometric object, such as obtained by cutting off pieces froma cylindrical strand, which optionally contains rounded edges and/orcorners. In a preferred embodiment, said pillows may have a substantialprismatic rectangular form with average dimensions (length/width/height)of about 40 mm×about 30 mm×about 12 mm, or about 20 mm×about 20 mm×about20 mm. In a more preferred embodiment, said pillows may have averagedimensions (length/width/height) of about 40 mm×about 20 mm×about 10 mm,most preferably of about 40 mm×about 15 mm×about 7 mm.

An individual form can weigh less than about 15 grams, or even less thanabout 10 grams.

Alternatively, the pillows may have a substantially cube like form. Alsosuch pillows may have rounded corners, thereby forming almost aspherical shape.

In another embodiment of the present invention, the “individual forms”are selected from at least one of coextruded ropes or rods, which do canbe of any length. Preferably, the coextruded ropes or rods may have alength between about 1 m and about 100 m, and more preferably betweenabout 5 m and about 50 m. In a preferred embodiment, the coextrudedropes or rods may have a diameter between about 0.1 cm and about 5 cm,preferably between about 1 cm and about 3 cm, and more preferably about2.5 cm. Preferably the coextruded ropes or rods are wound onto a reel orspool or are freely laid inside a box or other container.

According to the present invention, the packaged hot-melt adhesive has asubstantially tack-free surface and/or is free-flowing, preferably forextended periods of time, such as a month, 3 months, 6 months, a year,or more than a year. The packaged hot-melt adhesive may have a tack-freesurface and/or may be free-flowing at ambient conditions or roomtemperature, i.e. at temperatures from about 20° C. to about 25° C.,and/or at elevated ambient temperatures, i.e. at temperatures from about25° C. to about 70° C. The term “free-flowing” as used in the presentinvention means that “individuals” of the packaged hot-melt adhesive areable to move freely and without any difficulty and/or any agglomeration.Included in the definition “free-flowing” individuals are individuals,which do not fuse together and/or are able to move freely with none orminimal mechanical action and/or are mechanical separable.

E. Preparation of Individual Forms of a Packaged Hot-Melt Adhesive

The individual forms of a packaged hot-melt adhesive according to thepresent invention comprise a hot-melt pressure sensitive adhesivecomposition (a), which is covered by a coextrusion coating (b). Theinventive individual forms, particularly pillows or ropes may besubstantially tack-free and/or free-flowing.

According to one embodiment of the present invention, a method forpreparing individual forms of a packaged hot-melt adhesive according tothe present invention comprises the first step of providing a hot-meltpressure sensitive adhesive composition (a), and the second step ofcoextruding said adhesive composition (a) together with a coating (b) insuch way that the coating (b) at least partially covers the surface ofthe hot-melt pressure sensitive adhesive composition (a), therebyforming the individual forms of the packaged hot-melt adhesive andoptionally cutting the individual forms into pillows or prills.

The inventive method allows the preparation of tack-free and/or freeflowing individual forms of the packaged hot-melt adhesive.

Individual forms of the packaged hot-melt adhesive, particularly pillowsor prills, may be particularly suitable for use e.g. in vacuum feedersor similar conveying equipment due to their small size and weight.However, due to the larger surface of pillows or prills compared tolarger blocks, pillows or prills may have a higher tendency toagglomerate. Thus, the present invention is specifically advantageouswith small sized forms such as pillows or prills, although it mayequally work with pellets, flakes, blocks or any other form ofindividuals of the inventive packaged hot-melt adhesive.

The production of the individual forms of the packaged hot-meltadhesive, e.g. pillows or prills, may require multiple passes through aco-rotating twin screw extruder to homogenize the hot-melt pressuresensitive adhesive composition (a), followed by an coextrusion of theadhesive composition (a) together with the coating (b) through acoextrusion system, followed by a solidifying process optionallyfollowed by the calibration of the granules size.

Preferably, the packaged hot-melt adhesive according to the presentinvention is obtained by a coextrusion process, wherein the hot-meltpressure sensitive adhesive composition (a) is pumped through thecoextrusion head and wherein the coextrusion coating (b) is added to theadhesive composition (a) such that the coextrusion coating (b)substantially covers the adhesive composition (a) as a cover sheet.

Furthermore, the packaged hot-melt adhesive is obtained by a coextrusionprocess, wherein the coextrusion process comprises:

-   -   (i) providing one or more hot-melt components and blending the        hot-melt components to form a hot-melt pressure sensitive        adhesive composition    -   (ii) providing a coating material selected from neat low-density        polyethylene, neat polypropylene, or neat ethylene vinyl acetate        having a melt flow index between about 20 g/10 min and about 300        g/10 min.    -   (iii) coextruding both (i) and (ii) such that the adhesive forms        a strand substantially surrounded by the coating material    -   (iv) optionally cutting the resulting, coated strand of adhesive        (e.g. by forcing the composition past rotating blades and        cutting the hot-melt ribbons to form resultant individual forms)    -   (v) solidifying the individuals, optionally by cooling the        individuals by a liquid cooling medium or by a dry air        circulated.

Preferably, the individuals produced from this method are pillows orprills.

Hot-melt pressure sensitive adhesive compositions are suitable forpreparing the inventive hot-melt individuals as described above.Optionally, the packaged hot-melt adhesive individuals may compriseadditional components such as described above.

E. Use of Individual Forms

In one aspect of the present invention, a plurality of individual formsof a packaged hot-melt adhesive according to the present invention maybe used in an adhesive application process, wherein the packagedhot-melt adhesive is conveyed to a melting system in a free-flowingand/or air conveyable form before being molten and applied to asubstrate.

A disadvantage of individual forms of packaged hot-melt adhesivespreviously used is that said particular forms may fuse together insidethe adhesive containing containers, e.g. during storage. Such fusion ofindividual forms may occur, when said individual forms areconventionally bulk packaged, e.g. packaged in huge quantities inpouches or boxes. The elevated temperature, which may be present inwarehouses, combined with the weight of the pouches themselves, ifstacked upon each other, may cause that the conventional individualforms fuse together into a large entity or agglomerate. This completefusion of individual forms may result in that the corresponding packagedhot-melt adhesives may not be used in an adhesive application process,e.g. by conveying the packaged hot-melt adhesive to a melting system, afeeder or the like.

Therefore, it is an object of the present invention to provideindividual forms of the packaged hot-melt adhesive, which do not tack orfuse together during the shipping or storage process both at roomtemperature, as well as elevated temperatures and over time duringstorage. It is a further object of the present invention to modify thecoextrusion coating (b) of the packaged hot-melt adhesive to obtainindividual forms of the adhesive which have a significantly reducedfusion/blocking tendency, such that said individual forms stay looseand/or can be easily separated. It is a further object of the presentinvention to improve the individual forms of packaged hotmelt adhesives,in such a way that these adhesives can be packaged and automaticallyprocessed during an adhesive application process, i.e. during conveyingsaid individual forms during a melting process.

The individual forms of the package hot-melt adhesive according to thepresent invention do not tack or fuse together in a storage device at45° C. and remain substantially loose and free-flowing.

The term “substantially loose” means that the particles do not sticktogether or may be easily separated from each other if temporarilyblocking, by application of mechanical forces such as kicking againstthe container or vibration, or any other suitable methods.

With the packaged adhesive of the present invention, the plurality ofindividual forms does not fuse together as determined by a blockingtest.

In one embodiment of the present invention the individual forms of thepackaged hot-melt adhesive may be stored in an adhesive containingcontainer, e.g. a cardboard carton, a box, preferably a plastic box, aplastic bag, a pouch, a big bag or a supersack. These containers mightcontain between about 100 kg and about 1,000 kg of individual forms,preferably between about 400 kg and about 1,000 kg.

One aspect of the present invention encompasses an adhesive containingcontainer, comprising a plurality of individual forms of the packagedadhesive according to the present invention, wherein the container isselected from at least one of a box, preferably a plastic box, plasticbag, a pouch, a big bag, and a supersack.

The term “big bag” as used herein also encompasses the terms “supersack”, or “bulk bag”, which could be alternatively used in the contextof the present invention, and refers to bags made of textile or otherflexible material usable for shipping, handling and storing of flowableproducts. Such big bags are commercially available from e.g. PEMAVerpackung GmbH, Germany, preferably PEMA Article number 40-09999hb, invarious sizes and are conventionally used for larger amounts ofindividual materials, such as greater 100 kg to metric tons. Such bigbags also include reusable, recyclable and/or returnable versions of bigbags.

In one embodiment, the adhesive containing package bag comprises sealedbags. In a preferred embodiment, the adhesive containing package bag maybe chosen as a conical bottomed bulk bag/supersack or full drop or openbottom system, protected with s-flaps bulk bag/supersack. Preferably,said bags are made from out of coated 180+30 gr./sqm pp-woven-fabric.

In a typical adhesive application process, the individual forms areprovided from the container into a melting system, wherein saidindividual form are being transferred to the melter, wherein theindividual forms are molten and applied to a substrate.

In one embodiment of the present invention, the plurality of individualforms is conveyed to the melting system by vacuum conveying, tubulardrag conveying, a big bag conveying method, melt on demand, or anycombination thereof.

The vacuum conveying system is depicted in FIG. 1 and includes packagedhot-melt pressure sensitive adhesive which is inserted, e.g. by a bigbag (1), into a feed hopper (2) and the vibratory feeder (3). A vacuumpump (4) generates a vacuum in the vacuum conveyors separator tanks (5)and thereby sucks in air through the inlet point at the feed hopper (2),which in turn causes the packaged hot-melt adhesive to be aspirated andcarried in the corresponding air stream. Inside the separator tanks (5),a filter unit (6) separates the packaged hot-melt adhesive from the air,wherein the adhesive is contained in the separator tanks (5). When theseparator tanks (5) are filled with adhesive, the vacuum pump switchesoff, the pressure in the separator tanks is adjusted to the surroundingpressure and the adhesive material is discharged through a dischargevalve (7) directly into the hot-melt tank (8) to be charged. Thedischarge step is controlled by a load cell (9), which determines thatthe desired amount of adhesive is loaded into the hot-melt tanks (8).After the discharge step, the discharge valve (7) directly closes andthe complete conveying cycle restarts again.

An exemplary tubular drag conveying method, which refers to a discconveying system according to Cablevey Company, US, is depicted in FIG.2 and consists of a pipe (4) with the diameter of from about 7 cms toabout 13 cms, typically about 10 cm, through which the individual forms(6) are conveyed. The pipes are preferably stainless steel. The supersack (1) containing individual forms (6) can be discharged into aconical bottom feed hopper (2). Below the hopper discharge (2) is aninclined vibratory feeder (3). It can be useful to put a limit switch onthe vibratory feeder to control the rate at which the individual formsare fed into the tubular drag conveying system If the individual formsare fed in too quickly, blockages can occur. When the level in theadhesive melt tank (8) drops, the level transmitter sends a signal to acontroller and the controller then activates the vibratory feeder (3).Individual forms will flow out of the hopper (2), down the vibratoryfeeder (3) and into the tubular drag conveyor system. This systemconsists of a drive motor, pulleys and a cable (7). Every about 15 cm toabout 20 cm, along the length of the cable (7) are positioned plasticdiscs (5) that are roughly about 10 cm in diameter. The pillows (6) fillin the voids between the discs (5). The discs (5) are pulled slowlythrough the pipe line (4), conveying the individual forms (6) toward themelt tanks (9). The system can feed multiple melt tanks (9). Above eachmelt tank (9) is a rotating valve and drop section of pipe (8), down tothe melt tank (9). If that tank level is calling for feed, the valvespins (8) open and the pillows (6) fall into that melt tank (9). Whenthe level in the melt tank reaches a “full” set point, thecontroller/load cell (10) signals the valve (8) to spin closed and theflow of pillows to that tank stops. If the other melt tanks (9) on thissame system are also full, then the controller/load cell (10) will alsoturn off the vibratory feeder (3) and the disc conveyor system. When thenext melt tank requires additional adhesive the system turns on andcompletes the next cycle of feed. This tubular drag conveying system isvery gentle on the individual forms, and this is important because theindividual forms should not be damaged in any conveying system, or riskto spill out the adhesive and gumming up the feed system.

It has been found that when using a tubular drag conveying system forconveying individual adhesive forms, running at a lower than maximumcapacity provides sufficient throughput while decreasing the possibilityof adhesive plugs. The tubular drag conveying system can be run at lessthan about 50% capacity, less than about 30% capacity, less than about20% capacity or even from about 5% to about 50% capacity.

The individual form conveyed in the tubular drag conveying method can bea pillow. In embodiments, it is helpful if the pillow has a minimumthickness to prevent getting squeezed between the disc and the wall ofthe tube. It is useful if the pillow has a thickness of greater thanabout 0.318 cms (0.125 inches), at least about 0.635 cms (0.250 inches),or even from about 0.350 cms (0.138 inches) to about 1.5 cms (0.591inches).

An exemplary big bag conveying method according to the present inventioninvolves an adhesive containing container, selected e.g. as a big bag orsupersack, wherein the adhesive content of the container is manually orautomatically, e.g. by a crane or forklift, placed above a conical feedhopper. Typically, the big bag or supersack may contain manufacturedfracture sites in the material, which may cause the material tofracture, such that the big bag or supersack opens up at a definedlocation, e.g. at the bottom of the bag. The fractures sites aretypically generated in a way that the fracture only occurs upon aspecific impulse, e.g. by pulling a rope, which is attached to thefracture sites. By opening the bottom of the supersack, the adhesiveflows into the canonical feed hopper and from there directly into thepre-melter or into a further conveying system to reach the pre-melters.In the further adhesive application process, a fully or partiallyworking automated system similar to the systems described in the vacuumand tubular drag conveying method described above may be employed.

An exemplary melt on demand conveying method according to the presentinvention involves the individual forms being fed into an extruder (e.g.a single screw extruder) or other melting apparatus and then pumpedthrough a heated hose into at least one melt tank and optionally manymelt tanks found on separate manufacturing lines in the same location.Optionally, the molten adhesive can be fed directly in to one or moreadhesive nozzles. The individual forms can be fed into the extruder inany possible way including by use of a vibratory feeder.

In the present invention, the individual forms used in the vacuum,tubular drag and/or big bag conveying system according to the presentinvention are selected from the group consisting of pillows, prills,flakes or chips, preferably pillows.

Another aspect of the vacuum, tubular drag conveying and melt on demandmethods of the present invention is to avoid cross contamination. Duringa manual feeding process of individual forms of the packaged hot-meltadhesive, there is a possibility that the operator might feed the wronggrade of adhesive or a different adhesive into the melt tank. In theabove described automated conveying system, a bar coding or scanningelement may be included in the system that will alarm and minimize thelikelihood of using the wrong adhesive.

Another aspect of contamination is to allow ambient plant dust to enterthe melt tanks. This could result in “charring” and discoloration of thehot-melt adhesive as it's applied to the customer's product. Every timethe operator now opens the lid on the hot-melt tank, dust or otherforeign could enter the tank. The above-described automatic feed systemwould essentially be a closed system, thus minimizing the occurrence ofcontamination. With the current, manual feed practice, the melt tanklevels are typically cycled from full to fairly empty until beingrefilled. This results in a thin film of adhesive along the walls of theheated tanks that are exposed to significant heat history and couldresult in charring of the adhesive over time. In the described automaticfeed system, the level of adhesive is automatically controlled tomaintain the level consistently thereby avoiding high and low levels,and thereby minimizing the thin film heat history.

F. General Use of Packaged Adhesive

The packaged hot-melt adhesive according to the present invention can beused in the production of typical nonwoven hygiene articles, sanitarydevices, care articles, disposable medical drapes, paper, packaging,tapes and labels, furniture, textiles, footwear, in woodworking or inconstruction industries e.g. for roofing membranes or for otherconstruction type lamination.

Further, the packaged hot-melt adhesive according to the presentinvention can be used in the production of nonwoven hygiene and sanitaryarticles, non-woven articles, labeling, elastic lamination, constructionand core lamination or positioning adhesive. Also, the packaged hot-meltadhesive according to the present invention is used in the production ofdiapers, adult incontinence devices, sanitary napkins and disposablemedical drapes.

The packaged hot-melt adhesive according to the present invention mayalso be used in the production of disposable articles. Preferably, thepackaged hot-melt adhesive according to the present invention is used inthe production of at least part of the core of the disposable article orat least part of an elastic attachment attached to the disposablearticle.

The invention will now be described by way of the following examples.All parts, ratios, persons and amounts stated are by weight unlessotherwise specified.

EXAMPLES

In the context of the present invention, unless indicated otherwise, themelt flow index (MI) is determined in accordance with ASTM D 1238 at astandard temperature of 190° C. and at 2.16 kg load.

The viscosity is determined similar to method ASTM D-3236 as follows.The viscosity of a sample is determined using a Brookfield LaboratoriesDVH, DV-II, or DV-III Viscometer. The spindle used may be a SC-21,SC-27, SC-29 or SC-34 hot-melt spindle suitable for measuringviscosities in a range between about 100 mPas and about 4,000,000 mPas.The sample is placed in a pre-warmed measuring cell, which in turn isinserted into the heating element/container and is locked into place.The sample is heated until it is melted with additional sample beingadded until the melted sample is about 5 mm higher than the cylinder ofthe measuring spindle. The viscometer apparatus is lowered and thespindle is submerged into the sample. The viscometer is turned on andset to a shear rate that leads to a torque reading in the range of from30% to 60%. Readings are taken every minute for about 15 minutes oruntil the values stabilize. The final reading can be obtained after 30min and is recorded in mPas.

The molecular weight of all materials mentioned in this description, ifnot expressly stated otherwise, is determined by the method ASTM D4001-93/2006.

The melting point is determined according to DIN EN 1427 (Ring and Ball)with the Ring and Ball instrument MC753 as summarized as follows. Twoshouldered rings are heated to melt temperature and are placed onto asilicon-papered glass-plate and the melted substance is poured into therings. After cooling, the excess materials were cut off and the sampleswere placed into the sample holder of the apparatus and theball-centering guide with the balls is placed above the samples. A 600ml NF beaker is filled with 500 ml Glycerin and is placed on the heatingplate of the MC 753 apparatus. The frame, which is ready for measurementwith the shouldered rings, is placed into the beaker in such a way thatit is centered on the pins. The temperature sensor is adjusted in thetherefore designed opening in the frame and the MC 753 apparatus isactivated by choosing the measuring point (keyboard 1-10, basic unit).After a certain pre-heating time, the program automatically runs with aheating rate of 5° C. per minute until the balls fall. The measurementis completed when both balls have fallen down and two temperatures areshown on the display.

Polymer density is determined according to method ASTM D 1505.

The penetration number (PZ, “Penetrationszahl”) is determined by needlepenetration according to the test procedure is described in DIN 51579.About 100 g of sample polymer is melted until a temperature about 10 to15° C. above the melting temperature. The homogeneous melt is filledinto a corresponding examination cylinder, cooled at room temperaturefor about 1 hour and incubated at 25° C. for 1 hour. The melt-containingcylinder is placed in a pre-adjusted needle penetration device (mass:100 g, time: 5 sec, temperature: 25° C.). The needle is automaticallypositioned at the melt surface, the measuring process is started and thepenetration depth is recorded. For reproducibility three consecutivemeasurements are performed and the average value of the threemeasurements is recorded. The penetration number indicates the hardnessof the polymer composition and is referred to as 1/10 mm. Thereby a highpenetration number refers a soft material, wherein the low penetrationnumber refers to a hard material.

The blocking test 1 according to the present invention is performed byplacing 5 kg of coextruded individuals (e.g. pillows) of the product in3 bags. The particular containing bags were placed at 45° C. in a forcedair chamber for 2 hours. After the incubation period, the bags werestacked on top of each other. A 5 kg weight was placed on top of thestack of bags for 1 hour. Afterwards, the weight was removed and theindividual in the bags were evaluated according to the criteria set outbelow.

The blocking test 2 according to the present invention is performed byplacing 15 kg of coextruded individuals (e.g. pillows) of the product ina corrugated box with a lid. The box was placed at 30° C. in an oven for1 week. After the incubation period, the box was removed from the ovenand the pillows were dumped out and evaluated.

A rating system was developed, ranging from 1 to 5, to classify thepotential of co-extruded individual to not block during the furtherapplication in the melting process.

1: individual forms are completely fused together2: individual forms are mostly fused together3: individual forms partially fused together, cannot be separated bymechanical force4: individual forms are partially fused together, can be separated bymechanical force5: no fusion of individual forms observed

Example 1

A packaged hot-melt adhesive was prepared by using 1 wt % low densitypolyethylene (LDPE) with a melt flow index of 150 g/10 min and a roomtemperature density of 0.913 as the coextrusion coating material on astandard hot-melt pressure sensitive adhesive having a mineral oilcontent of 20.6 wt % and a 15 wt % polystyrene containing linearstyrene-isoprene-styrene block copolymer (MW 220,000, couplingefficiency 81%, Kraton D-1161 NS). The results are shown in Table 1below.

Example 2

A packaged hot-melt adhesive was prepared by using 2 wt % low densitypolyethylene (LDPE) with a melt flow index of 150 g/10 min and a roomtemperature density of 0.913 as the coextrusion coating material on astandard hot-melt pressure sensitive adhesive having a mineral oilcontent of 27 wt % and ethylene-octene copolymer (ENGAGE 8200, DowChemical Company). The results are shown in Table 1 below.

Example 3

A packaged hot-melt adhesive was prepared by using 2 wt % low densitypolyethylene (LDPE) with a melt flow index of 150 g/10 min and a roomtemperature density of 0.913 as the coextrusion coating material on astandard hot-melt pressure sensitive adhesive having a mineral oilcontent of 16 wt % and a metallocene-synthesized low molecular weightpolypropylene polymer (L-MODU S-400, Idemitsu Kosan Co., Ltd.). Theresults are shown in Table 1 below.

The following comparative examples are included.

Comparative Example 1

A packaged hot-melt pressure sensitive adhesive was prepared bycoextruding a standard hot-melt pressure sensitive adhesive having 26.5wt % of mineral oil and ethylene-octene copolymer (ENGAGE 8200, DowChemical Company) coextruded with 2 wt % of a coating composition, whichin turn comprises 40.0 wt % hydrogenated microwax (ShellMicrocrystalline Wax HMP, Shell), 35.9 wt % of cycloaliphatichydrocarbon resin tackifing agent (ESCOREX 5320, Exxon Mobil Company),23.9 wt % of styrene ethylene butylene styrene block copolymer (SEPTON8007, Kuraray America, Inc.). The results are shown in Table 1 below.

TABLE I Example No. 1 2 3 Comp. 1 Viscosity at 150° C. 2,800 4,800 5,9004,800 [mPas] Melting point [° C.] 93 94 104 94 Melt index of polymer 150150 150 — coating Blocking test results (1)^(x) — 3 5 1 Blocking testresults (2)^(x) — 5 — 1 ^(x)Blocking test results 1: individual formsare completely fused together 2: individual forms are mostly fusedtogether 3: individual forms are partially fused together, cannot beseparated by mechanical force 4: individual forms are partially fusedtogether, can be separated by mechanical force 5: no fusion ofindividual forms observed

According to table 1, the neat LDPE coating according to the presentinvention, which is used in Examples 1, 2 and 3 in an amount of 1 wt %and 2 wt % results in superior results in blocking tests compared to theconventional coating composition used in Comparative Examples 1 and 2,irrespectively of the base polymer used.

Moreover, a direct comparison of the composition of Example 2 with thecomposition of comparative example 1, wherein the type of base polymerand the amount of plasticizer of the hot-melt pressure sensitiveadhesive are identical, shows improvement in blocking test of the neatLDPE coating in comparison with the conventional coating materials.

The following table 2 provides comparative examples A, B, C and D withexamples 1, 2 and 3, and discloses different polymers, comprisingvarying amounts of plastizicer in relation to the correspondingpenetration numbers (PZ).

TABLE II Example No. Comp. A 3 Comp. C Comp. D 2 Comp. E 1 PolymerKraton L- Vector Taipol EG- Vector Kraton type D1117¹ MODU 4411³ SBS-8200⁴ 4114A⁵ D1161 S400² 320 NS⁶ Plasticizer 5 16 18 25 26 26 21-26content [wt %] PZ [25° C.] 63 32 34 62 51 132 117 PZ:Penetrationszahl/Penetration number ¹Kraton D1117 - available fromKraton Polymers U.S. LLC; 17% Styrene, MFR = 33 g/10 min @200° C., 5 kg;33% diblock ²L-MODU S-400 - metallocene catalyzed polypropyleneavailable from Indemitsu Kosan Co. Ltd. Viscosity @190 C. = 7000 cp³Vector 4411A - available from Dexco Polymers; 44% Styrene, MFR = 40g/10 min @ 200° C., 5 kg; <1% diblock ⁴EG-8200 - metallocene catalyzedethylene octene available from Dow Chemical Company, MI = 5.0 g/10 min,190° C., 2.16 kg ⁵Vector 4114A - SIS available from Dexco Polymers; 15%Styrene, MFR = 25 g/10 min @ 200° C., 5 kg; diblock content = 42%⁶Kraton D 1161NS - SIS available from Kraton Polymers U.S. LLC; 15%Styrene, MFR = 9 g/10 min @ 200° C., 5 kg; diblock content = 33%

The above specific examples are not intended to limit the presentinvention. Rather, other embodiments are within the appended claims.

1. A method of using a hot melt pressure sensitive adhesive inindividual forms comprising the steps of: a.) obtaining coextruded hotmelt pressure sensitive adhesive in individual forms; and b.) conveyingthe hot melt pressure sensitive adhesive to a melting system by use of aconveying system selected from the group consisting of a tubular dragconveying system and a melt on demand conveying system.
 2. The method ofclaim 1 wherein the coextruded hot melt pressure sensitive adhesive inindividual form is fed into the conveying system by use of a vibratoryfeeder.
 3. The method of claim 1 wherein the conveying system is atubular drag conveying system.
 4. The method of claim 1 wherein the hotmelt pressure sensitive adhesive in individual form is a pillow with athickness of at least about 0.635 cms (0.250 inches).
 5. The method ofclaim 1 wherein the hot melt pressure sensitive adhesive comprises apropylene polymer.
 6. The method of claim 1 wherein the hot meltpressure sensitive adhesive has an average penetration number (PZ),which is between about 20 and about
 70. 7. The method of claim 1 whereinthe hot melt pressure sensitive adhesive is conveyed to more than onemelting system.
 8. The method of claim 1 wherein the hot melt pressuresensitive adhesive is provided in the individual form selected from thegroup consisting of a pillow, a prill and a coextruded rope.
 9. Themethod of claim 1 wherein the hot melt pressure sensitive adhesivecomposition comprises a base polymer selected from the group consistingof polyolefins, polyolefin copolymers, polyolefin/alpha-olefininterpolymers and synthetic rubbers.
 10. A method of providing moltenadhesive comprising: a. providing a plurality of individual forms of acoextrusion coated hot melt pressure sensitive adhesive wherein the hotmelt pressure sensitive adhesive has an average penetration number (PZ),which is between about 20 and about 70; b. conveying the plurality ofindividual forms to a melting system; c. heating the plurality ofindividual forms until they become a molten adhesive; and d. applyingthe molten adhesive to a substrate.
 11. The method of claim 10 whereinthe plurality of individual forms have a rating of at least 3 whentested according to blocking test
 1. 12. The method of claim 10 whereinthe plurality of individual forms are continuously conveyed to themelting system so as to maintain a consistent level of adhesive in themelting system.
 13. The method of claim 10 wherein the plurality ofindividual forms are conveyed with a tubular drag conveying system. 14.The method of claim 10 wherein the plurality of individual forms areconveyed with a melt on demand conveying system.
 15. The method of claim10 wherein the coextrusion coating is neat low-density polyethylene. 16.The method of claim 15 wherein the neat low-density polyethylene has amelt flow index between about 20 g/10 min and about 300 g/10 min. 17.The method of claim 10 wherein the hot melt pressure sensitive adhesivecomprises a propylene polymer.
 18. The method of claim 10 wherein thesubstrate is a non-woven.
 19. The method of claim 10 wherein the hotmelt pressure sensitive adhesive comprises less than about 20 wt %plasticizer.
 20. The method of claim 10 wherein the hot melt pressuresensitive adhesive composition comprises a polypropylene polymer.